This invention relates to a system for judging boundary lines in sporting events, such as tennis, for automatic officiating of the game.
Today, all sporting games involving rules around boundaries depend on the (often-controversial) decisions of human judges. Unfortunately, as technology has helped the athlete and even the causal player perform at greater levels, a human being""s ability to judge a boundary line has not increased. Thus, at the competitive level there has been an increasing frequency in such controversial decisions.
For the recreational athlete, a game like tennis relies on the player making the in or out call at the boundary line and the opposing player trusting that call. This is unfortunately fraught with difficulties and many players feel the overwhelming need to cheat, or indeed to accuse their opponent of cheating.
In either case, there exists a strong need for a commercially viable system for judging the boundary lines in such a game. Since it can readily be appreciated that these problems are not unique to the game of tennis, a system which could work for other sports with little or no modification would be highly desirable. Also, in order to be commercially viable, especially at the competitive level, such a system must not require any changes to the court, the players"" equipment or the ball and must not intrude upon the play of the game itself.
The applicant is aware of several attempts to design and patent a system, each of which appears to have had little if any commercial success and each of which suffers from significant deficiencies.
One such system is described in U.S. Pat. No. 5,489,886 of Wexler et al. That system requires up to 30 specially designed cameras to monitor the court and feed data into a processor. Given the huge amount of data generated by 30 such cameras, a super computer would be required. The Wexler et al. system also requires a camera placed under the net, in addition to the camera placed on each of the lines, which could interfere with the normal play of the game. The cost of such a system, if it worked, would be prohibitive to all but the hosts of the world""s largest tournaments, such as Wimbledon. To the applicant""s knowledge, however, this system did not work, and has never worked acceptably because of the lack of a suitable computer processor for the task.
Other examples known to the applicant include U.S. Pat. No. 4,432,058 of Supran, which requires that the ball be conductive and the court be equipped with electrical circuits, U.S. Pat. No. 4,866,414 of Diaconu et al. which requires the players to adapt their shoes and socks to the system and U.S. Pat. No. 4,893,182 of Gautrand et al., which is designed for a static scene such as a bowling alley and thus would not function in a high speed game such as tennis.
It is therefore an object of the present invention to provide a system and method for judging boundary lines, which system is capable of processing and interpreting the movements of objects (most often balls), at potentially high speeds, thus enabling the automatic overseeing and judging of sporting games. The system can be used for many different types of games, from tennis, volleyball, soccer or hockey, to sports not involving balls but requiring the clear identification of boundaries. The process can be adopted to evaluate and judge the adherence to the given rules of a sport.
In one aspect of the invention there is provided a system for judging boundary lines on a court in sporting games, for determining whether a ball in play bounces in or out of court. The system comprises at least one camera to capture movement of the ball and a frame grabber associated with each of the cameras to process the movement as captured frames. An image processing system is configured to receive the captured frame from the frame grabbers and to process the captured frame as images to determine whether the ball is in or out of court and to generate a signal if the ball is out of court. There is an output device coupled to the image processing system to receive the signal and alert the players.
In another aspect of the invention, the cameras are equipped with auto-iris lenses to automatically adjust the aperture of the cameras.
In another aspect of the invention, the camera may be color or high speed black and white.
In another aspect of the invention, the image processing system comprises a calibration sub-system and a recognition sub-system.
In another aspect of the invention, the calibration sub-system comprises a line recognition module, an image segmentation and region grouping module, a court line and region registration module, a supervised ball recognition module and a look-up-table module.
In another aspect of the invention, the recognition sub-system comprises a frame/sequence control module, a motion tracking module, an unsupervised automatic ball recognition module, a trajectory fitting module, a bounce detection module and an in/out judge module.
In another aspect of the invention, there is provided a method of judging boundary lines on a court in sporting games in order to determine whether a ball in play bounces in or out of court in which the method utilizes at least one camera to capture movement of the ball, a frame grabber associated with each of the cameras to process the movement as captured frames and an image processing system configured to receive the captured frame from the frame grabbers and to process the captured frame. The method comprises the steps of:
selecting a mode of game using an input device configured so as to control the system and commence a recognition sub-system;
during play of the game, continuously capturing image frames from the frame grabbers;
within the image frames locating and isolating moving objects;
comparing the moving objects to a calibrated image of the ball so as to filter out any moving object which is not the ball;
fitting a path of the ball into a connected trajectory;
detecting a spot on the court where the ball bounces by locating within the trajectory a sudden change in direction and by fitting or calculating the coordinates of the bounce;
determining whether the ball is in or out of court;
transferring a signal to an output device if the ball is determined to be out of court.